In the semiconductor industry, plasma processing chambers are used to perform various plasma processing techniques. Such techniques include, for example, low temperature plasma etching, low temperature plasma ashing, and plasma chemical vapor deposition. Some plasma processing chambers include a cylindrical ceramic ring located in between top and bottom electrodes. In such chambers, applied radio-frequency (RF) power is dissipated not only in the plasma but also in the ceramic ring, which may lead to unwanted power dissipation when the dielectric constant and phase delay of the ceramic ring are high.
When a specific ceramic is chosen, the imaginary part of the dielectric constant is relatively constant from one sintering bunch to another. However, the real part of the dielectric constant may scatter over a wide range. To ensure uniform quality of ceramic structures, ceramic makers perform sample tests to measure the dielectric properties of the material. However, these tests are destructive as they are based on removal of a portion of the ceramic structure. Moreover, the tested portion is generally small and at best yields a local value of the dielectric constant that is not representative of the ceramic structure as a whole.